The current standard of care for epidural blockades and related spinal anesthesia procedures is manual palpation of spinal bone landmarks followed by blind needle insertion. However, in the obese segment of the population, estimated at approximately 33% of the total US population, spinal bone landmarks are covered with thick layers of fat and are not detectable with palpation. As a result, first-pass failures occur at high rates (i.e. 40-80%), which results in increased rates of incomplete anesthesia, higher pain scores, and significantly lower patient satisfaction. Health complications also result, including: headache, bleeding, back pain, high spinal, and paralysis. While recent studies have shown that ultrasound guidance can improve success rates, failure rates remain high and the blind method remains standard of care. The lack of widespread acceptance for ultrasound guidance is largely due to technical challenges associated with ultrasound imaging of bone structures. Several studies have demonstrated that the utility of ultrasound guided epidurals correlates strongly with user familiarity and that most anesthesiologists are unable to reliably interpret the spinal anatomy using current medical ultrasound technology. During the Phase I project, the feasibility of a low-cost, handheld ultrasound system and new technologies was demonstrated in an ex vivo whole pig lumbar spine model. This Phase II proposal seeks funding to support the continued development of a low-cost, handheld medical device for neuroaxial anesthesia guidance in the obese. The key technological innovations of this project are focused on improvements to ultrasound- based bone visualization and include a new spinal bone imaging approach that enables the automatic detection of spinal bone landmarks and needle injection site. The long-term goal of this project is to demonstrate a portable, low-cost, ultrasound-based medical device that facilitates neuroaxial anesthesia in the obese, improves success rates, and lowers the risk of associated health complications. The Phase II hypothesis is that the handheld medical imaging device and associated technologies increases first-attempt epidural anesthesia success rates, defined as successful epidural administration on the first needle insertion attempt, in the obese. A new low-channel count ultrasound transducer design for improved bone imaging performance will be designed, fabricated, and tested. In addition, ultrasound imaging technologies central to this project will be optimized, integrated into the new device, and validated in a clinical study across a range of body mass index (BMI). Finally, the Phase II hypothesis will be directly tested in an 80 patient clinical study. With an estimated 22 million epidural and related procedures performed in the US per year, the estimated US market size for the proposed device is $234 M/yr.